Poor quality in indoors..

The quality of the FZ150 is very inconsistent and swinging in low light indoors pics.

I tried the "presets" like handheld night shot and so on, and others also in P Mode with different ISO.

The images lose a lot of details, I mean a lot... not only because of the noise, that it's not that bad.
The quality in normal light is excellent (except blowing highlights sometimes)

I do not expect DSLR capabilities, but there are time when 800 ISO is very good and other where 800 ISO is awful.
The skin of the persons in the pics is "pixellated alike"
What's the trick for low light indoors pics with "acceptable" quality?
--
Ignorant photograph beginner